Corrosion inhibitor



' Patented Aug. 10, 1937 NITED STATES PATENT OFFICE 1 CORROSION INHIBITOR No Drawing.

Application September 10, 1934,

Serial No. 743,493

14 Claims.

This invention relates to the prevention of corrosion of metals, and refers more particularly to a new and improved treatment of hydrocarbon oils containing sulfur. It includes both the 5 method of treatment and the product obtained.

More specifically this invention relates to the treatment of hydrocarbon liquid fuels ranging from liquefied petroleum gases through kerosene to prevent or retard or inhibit the corrosive action of elementary sulfur on such metals as copper, bronze, etc.

Gasolines as commercially produced always contain more or less elementary sulfur resulting rom the oxidation or decomposition of hydrogen sulfide and/or organic sulfur compounds during fractionation or other heat treatment of these products. Furthermore, during the doctor sweetening operation wherein free sulfur is added to the oil for the purpose of converting the lead mercaptides to lead sulfide and alkyl disulfides tained in a reasonable amount of time. Therefore, regardless of how the oils are produced some free sulfur is practically certain to be present and such sulfur reacts readily with copper and its alloys when the said oils are in contact with such metals.

Similar problems or disadvantages are met with liquefied petroleum gases which is the name applied to a,material similar to gasoline in physical properties but which consists largely of low boiling hydrocarbons such as propane and butane which are kept in the liquid state by the use of pressure. If such liquefied gases are drawn oil in the vapor form then free sulfur will be concentrated in the containers and over a period of time the quantity may become quite large. It is common practice in dispensing liquefied petroleum gases to use certain materials containing copper V and its alloys, and such materials are particularly subject to corrosion by free sulfur. This corrosion'and consequent weakening of the materials is especially dangerous where such ele- 5 vated pressures are necessary.

At the present time it is necessary to treat the crude hydrocarbon products by very rigorous and expensive methods in order.'that the quantity of free sulfur present in the finished products is sufliciently low that the rate of corrosion will not be exorbitant.

I have now discovered that by the addition of small amounts of certain compounds to the free sulfur containing hydrocarbon oils the corrosive action of the sulfur on such metals as copper and its alloys is prevented or retarded or inhibited. I have found that the organic compounds of the general formula CH2OHCH2-OR wherein R is either an alkyl, aryl, acyl or benzoyl radical, are particularly effective for this purpose. Such compounds are generally referred to as the mono-alkyl or aryl ethers and esters of the glycols. I havediscovered that ethylene glycol mono-ethyl ether is particularly outstanding in its effectiveness in preventing or retarding or inhibiting the action of free sulfur on copper.

Ethylene glycol is commonly thought to be insoluble in light hydrocarbon oils, nevertheless I have found that when a few drops of this compound is added to and/or left in contact with a hydrocarbon oil containing free sulfur that such. free sulfur does not corrode copper surfaces. I have found glycerin, also, to be effective for this purpose.

Other compounds such as propylene and butylene glycols and their mono-alkyl and aryl ethers and esters when added to hydrocarbon oils prevent or retard or inhibit the free sulfur in such oils from reacting with copper and its alloys. The derivatives of diethylene glycol and triethylene glycol can likewise be used in this invention.

According to this invention a small amount of one of the compounds mentioned, e. g. ethylene glycol mono-ethyl ether, is added to a hydrocarbon oil containing elementary sulfur. In general the preferred actual concentration of the compound may vary between the limits of 0.001 percent to 0.1 percent. Such quantities give good results but larger or smaller amounts of the glycol compound may be used without departing from the scope of this invention.

The amount of the glycol compound needed to prevent corrosion of the copper depends to some extent on the amount of free suliur in the hydrocarbon solution. .The percent of the compound to be used in the oil depends also on the ratio of the surface area of the copper to the volume of the oil.

It is to be understood that the corrosion-preventing agent may be added either to a hydrocarbon oil already containing free sulfur or to an oil which may subsequently contain elementary sulfur as a result of the decomposition and/ or the oxidation of unstable sulfur compounds therein.

I have found that the various compounds are not equally effective and that much larger quan titles of certain of the compounds must be used if equivalent effectiveness is to be obtained. The results indicate (1) that in general the ethers l are more effective than the esters and (2) that the simple alkyl groups such as the methyl and ethyl are considerably better than the butyl or benzyl group.

One of the tests used for evaluating the effectiveness of these compounds is the corrosion test wherein a clean copper strip is immersed in the hydrocarbon oil and heated to F. for several hours. The length of the heating period before appearance of discoloration on the copper strip is the measure of the corrosiveness of the oil.

Another test is merely that of noting the time.

during which no discoloration appears on the copper strip immersed in a naphtha solution at room temperature.

The following examples will illustrate the practice of the invention:

Example 1.-Fifty cc. of a naphtha containing 0.00086 percent elementary sulfur and 0.01 percent ethylene glycol mono-ethyl ether showed no discoloration on a copper strip even after heating for 3 hours at 140 F. An untreated sample was almost immediately corrosive to copper.

Example 2.-0.00086 percent elementary sulfur was added to a freshly distilled light naphtha. A copper strip immersed in a 60 cc. portion of this naphtha was quite badly corroded after twenty minutes at room temperature whereas a copper strip immersed in a similar portion of the naphtha to which was added 0.002 percent ethylene glycol mono-ethyl ether showed no discoloration or corrosion at the end of 78 days.

Example 3.A 60 cc. portion of naphtha containing 0.00086 percent elementary sulfur gave a badly corroded copper strip at the end of fifteen minutes at room temperature whereas a similar portion of the naphtha to which was added approximately 0.014. percent of ethylene glycol mono-acetate had produced no discoloration on a copper strip when noted at the end of two days. After standing for 66 days the only corrosion evident constituted several tiny black spots about the size of pin points, really a negligible amount.

Example 4.A 60 cc. portion of naphtha containing 0.00086 percent elementary sulfur gave a badly corroded copper strip at the end of fifteen minutes at room temperature whereas a similar portion of the naphtha to which was added 0.024 percent of ethylene glycol mono-benzyl ether showed no discoloration on the copper at the end of 48 hours.

Example 5.A little ethylene glycol (0.014 percent by volume) was put into a bottle with a light naphtha containing 0.00086 percent elementary sulfur. No corrosion or discoloration could be detected on the copper strip after being im mersed in the naphtha for ten days.

Example 6.-A couple of drops of glycerin were placed in a bottle of naphtha containing 0.00086 percent elementary sulfur. A copper strip in this naphtha showed no discoloration at the end of 65 days.

Example 7.-A drop of triethylene glycol was placed in a bottle of naphtha containing 0.00086 percent elementary sulfur. A copper strip in this naphtha showed no discoloration at the end of 17 hours. After 29 hours, however, several black spots hadappeared.

Trimethylene glycol in a similar test gave an inhibitionperiod equivalent to approximately two days.

Example 8.-0.002,'1Jercent of ethylene glycol mono-butyl ether prevented corrosion of copper in a naphtha solution containing 0.00086 percent elementary sulfur indefinitely (more than 78 days) whereas 0.0018 percent of the butyl ether was hardly effective at all. However, a larger quantity of the butyl ether (0.024 percent) was sumciently effective that only a little corrosion was noted at the end of 48 hours.

In a similar test the benzyl ether was found to be several times as efiective as the butyl ether.

It is not desired to limit the invention to the concentration of -the treating agents given in the above examples. Use may be made of higher or lower concentrations of any members of the classes of compounds mentioned herein and as a result thereof longer or shorter periods of pre-- venting, retarding or inhibiting corrosion of copper and. its alloys by elementary sulfur secured depending upon the specific agent used, the concentration of the agent, the percentage of free sulfur in the material treated and the conditions under which the subsequent storage takes place.

Obviously these various glycol compounds differ greatly in their solubility in hydrocarbon oils. Some of them are practically insoluble while others are readily soluble. Inasmuch as the desired solubility can usually be obtained by the introduction of more oil soluble or less oil soluble groups into such compounds, it is to be understood that such may be made without departing from the spirit and scope of this invention. Miscibility agents such as butyl alcohol can likewise be added with the more insoluble compounds like ethylene glycol or glycerin to increase their solubility in the hydrocarbon oils.

I claim:

1. The method of inhibiting the corrosion of copper and its alloys by hydrocarbon liquid fuels ranging from liquefied petroleum gases through kerosene, said liquid fuels containing sufiicient elementary sulfur so that they tend normally to corrode copper and its alloys, which comprises adding to the said liquid fuels a small amount of a compound of the structure RO(CH2) m(CH2O-- CH2) x-(CHOH) n-H wherein R represents a member selected from the group consisting of the alkyl, aryl, acyl and benzoyl radicals and wherein x represents an integer from the group 0, 1 and 2 and m represents an integer from the group 1, 2 and 3 and n represents an integer from the group 1 and 2.

2. The method of inhibiting the corrosion of copper and its alloys by hydrocarbon liquid fuels ranging from liquefied petroleum gases through kerosene, said liquid fuels containing sufficient elementary sulfur so that they tend normally to corrode copper and its alloys, which comprises adding to the said liquid fuels a small amount of a compound of the structure kerosene, saidliquid fuels containing sumcient elementary sulfur so that they tend normally to corrode copper and its alloys, which comprises adding to the said liquid fuels 2. small amount of a compound of the structure wherein R represents a member selected from the group consisting of the alkyl, aryl, acyl and benzoyl radicals and wherein m represents an integer from the group 1, 2, and 3 and n represents an integer from the group 1' and 2.

4. The method of inhibiting the corrosion of copper and its alloys by hydrocarbon liquid fuels ranging from liquefied petroleum gases through corrode copper and its alloys, which comprises adding to the said liquid fuels a small amount of ethylene glycol mono-ethyl ether.

6. The method of inhibiting the corrosion of copper and its alloys by hydrocarbon liquid fuels ranging from liquefied petroleum gases through kerosene, said liquid fuels containing sufilcientelementary surfur so. that they tend normally to corrode copper and its alloys, which comprises adding to the said liquid fuels a small amount of ethylene glycol mono-acetate.

"l. Predominantly hydrocarbon liquid fuels ranging from liquefied petroleum gases through kerosene containing suificient elementary sulfur to tend normally to corrode copper and its alloys to which has been added as a corrosion inhibitor a small amount of a compound of the structure CHz).-.-(CH OH)fl--H wherein R represents a member selected from the group consisting of the alkyl, 'aryl, acyl and benzoyl radicals and wherein a: represents an integer from the group 0, 1 and 2 and m represents an integer from the group 1, 2 and 3 and n represents an integer from the group 1 and 2.

8. Predominantly hydrocarbon liquid fuels.

ranging from liquefied petroleum gases through kerosene containing sumcient elementary sulfur to tend normally'to corrode copper and its alloys to which has been added as a corrosion inhibitor a small amount of a compound of the structure wherein R. represents a member selected from m sents an integer from the group 1, 2 and 3.

9. 1:17 hydrocarbon liquid fuels ranging from liquefied-petroleum gases through kerosene containing sumcient elementary sulfur to tend normally to corrode copper and its alloys to which has been'added as a corrosion inhibitor a small amount of a compound of the structure wherein R represents, a member selected from the group consisting of the alkyl, aryl, acyl and benzoyl radicals and wherein m represents an integer from the group 1, 2, and 3 and n represents an integer from the group 1 and 2.

10. Predominantly hydrocarbon liquid fuels ranging from liquefied petroleum gases through kerosene containing sufficient elementary sulfur to tend normally t'o corrode copper and its alloys to which has been added as a. corrosion inhibitor a small amount of a compound selected from the group consisting of the mono-'alkyl and monoaryl ethers and esters of ethylene glycol.

11. Predominantly hydrocarbon liquid fuels ranging from liquefied petroleum gases through kerosene containing sufilcient elementary sulfur to tend normally to corrode copper and its alloys to which has been added as a corrosion inhibitor a small amount of ethylene glycol mono-ethylether.

fur to tend normally to corrodecopper and its alloys to which has been added as a corrosion inhibitor a small amount of a compound selected from the group consisting of the mono-alkyl and mono-aryl ethers and esters of ethylene glycol.

14. Liquefied petroleum gases containing sufllcient elementary sulfur to tend normally to corrode copper and its alloys to which has been added as a corrosion inhibitor a small amount of a compound of the structure waurna a; scnmzE. 

